Red List assessment 583
FIG. 1 The distribution (black outline) of (a) salmon gum Eucalyptus salmonophloia in western Australia, and (b) poplar box Eucalyptus populnea in eastern Australia, with uncleared forest and unambiguous deforestation. In areas where deforestation has not been mapped it was assessed using random points and is identified by ,5% tree cover in an area subject to clearing (Fensham et al., 2020). Cleared areas with .5% tree cover are conservatively assumed to be forested.
Protection (Clearing of Native Vegetation) Regulations 2004 under the Environmental Protection Act 1986 and it seems probable that the more extensive, eastern part of the species’ range will be preserved into the future. In the relatively mesic, western part of the species’ range, salmon gum woodlands occur on loam soils on which wheat crops are now grown. Isolated trees in paddocks and many small woodland fragments continue to decline and there is little regeneration (Yates et al., 1994a). Importantly however, sub- criterionA2 applies over the past three generations and carries no assumptions about future decline. If the population decline of salmon gum stabilizes it would be disqualified as a threat- ened species (i.e. no longer Vulnerable) by 2073 (Fig. 2). Like salmon gum, poplar box also occurs on arable soils,
but with a more extensive geographical range (859,189 km2; Fig. 1). Unlike salmon gum, deforestation has occurred throughout the range of the species (Fig. 2), progressing north- wards and intensifying in these regions from1970 (Fensham& Fairfax, 2003). Legislation currently regulates habitat loss asso- ciated with agriculture in both Queensland and New South Wales, but clearing continues at high rates (Queensland Department of Environment and Science, 2018; Audit Office of New SouthWales, 2019). For poplar box, a plausible, hypo- thetical scenario could assume rapid population decline is abated but slower declines continue (Fig. 2). This seems likely because even if clearing controls were completely effective in the future, areas with residual regrowth are likely to be further developed for more intensive use and livestock grazingwill in- hibit regeneration in areas not subject to clearance (Weinberg et al., 2011). Under this scenario, poplar box will be downlisted from a threatened status in 2130 because its rate of decline will eventually become ,30% overthree generations(Fig. 2). Imagine a future human population explosion in Australia
alongside subsequent demands for increased intensive land use, together with an Australian society that has little regard for preserving natural
habitat.Remnant poplar box woodlands could again become especially attractive for development of croplands and pasture. Under this scenario (Fig. 2), poplar box would undergo rapid population declines exceeding 30% in three generations and requalify as threatened in 2440. In the case of widespread common species these fluctuations in land-use and population declinemay continue for a millen- nium before they requalify for categorization as threatened under criteria B, C or D (Fig. 2). The application of subcriterion A2 to widespread and
common species such as salmon gum and poplar box can seem misguided when much rarer species without decline do not qualify for listing as threatened (Fensham et al., 2020). However, the accuracy of A2 as a measure of extinc- tion risk is apparent when the potential future scenarios are presented (Fig. 2). If decline is arrested, then a species eli- gible as threatened under A2 will be appropriately disquali- fied. If decline is only marginally.30%in three generations and further decline has been abruptly arrested, disqualifica- tion occurs shortly after qualifying (e.g. salmon gum, Fig. 2). If listing as threatened provides a mechanism for reducing decline, a downlist in status to not threatened is appropriate. If decline is diminished, time to ineligibility as a threatened species can be calculated using the formula:
G2 =
0.7(3R1)−0.3A0 +GRY(R1 −R2) 0.7R1 −R2
whereG2 is the year of disqualifying from a threatened status (in generations from time = 0), R1 is the initial decline rate (amount per generation expressed as a positive number) prior to the reference year GRY, R2 is the diminished decline
Oryx, 2022, 56(4), 581–586 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605320001325
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